Secondary throttle control for two-stage carburetor



Ayn-i130, 1957 H. A. CARLSQN EI'AL SECONDARY THROTTLE CONTROL FOR TWO-STAGE ARBURETOR Filed Feb. 15, 1954 2 Shoots-Shut 1 INVENTOR. HAROLD A.CARLSON JAME S T.W. MQSELEY ATTORNEY April 30, 1957 H. A. CARLSON ETAL 2,790,631

SECONDARY THROTTLE CONTROL FOR wo s'mcsz CARBURETOR Filed Feb. 15, 1954 2 Shuts-Shoot 2 2 3 l7 J. l5

l6 la 34 F INVENTOR.

HAROLD A. CARLSON BY JAMES T.w. MOSELEY ATTORNEY SECONDARY THROTTLE CONTROL FOR TWO-STAGE CARBURETOR Harold A. (larlson, Brentwood, and James T. W. Moseley, Richmond Heights, M0., assignors, by mesne assignments, to ACE Industries, Incorporated, New York, N. Y., a corporation of New Jersey Application February 15, 1954, Serial N 0. 410,299

12 Claims. (Cl. 26123) This invention relates to multi-stage carburetors for internal combustion engines of the automotive type and consists particularly in novel means for controlling the actuation of the secondary throttle valve.

vWhere thesecondary throttle in a two-stage carburetion system is opened automatically, as by direct action of air flow or by a suction motor device rather than by a positive linkage connection to the primary throttle, there has been a rather diflicult problem in insuring tight closing of the secondary throttle against its stop during idling without unduly increasing the resistance to opening of the secondary throttle. The present invention teaches a way of overcoming this problem which involves utilizing, for closing the secondary throttle, a spring which is stressed between actuating levers movable with the primary and secondary throttles, respectively, in such a manner that the resistance to opening of the secondary throttle is greatest when the pirmary throttle is fully closed and decreases as the primary throttle is opened. Such a spring applies its maximum closing pressure to the secondary throttle, when the primary throttle is fully closed, as is desirable, while oflering no resistance to opening of the primary throttle.

In the accompanying drawings which illustrate the invention,

Fig. 1 is a side view of a two-stage carburetor embodying the invention and showing the throttle valves both fully closed.- I

Fig. 2 is a partial side view of the device in Fig. 1 and showing the throttle valves partially opened.

Fig. 3 is a view of the parts in Fig. 2, but showing both throttle valves fully opened.

Fig. 4 is a top view of the structure in Fig. 3.

The carburetor shown in Fig. 1 is of the downdraft type having primary and secondary mixture conduits 6 and 7 including the usual Venturi tubes into the smallest of which open primary and secondary main fuel nozzles 8 and 9. A choke valve 10 is mounted in the air inlet portion 11 of the primary mixture conduit and is controlled by Well-known automatic mechanism located within a housing 12. In the outlet portions of the conduits are primary and secondary throttle valves 13 and 14 mounted on shafts 15 and 16 having control levers 17 and 18 secured to corresponding ends thereof. At the opposite end of primary throttle shaft 15 there is provided the usual manual control lever (not shown). Fuel for idling is supplied through idling passages 19 and 2t) and 21 and 22 terminating in idling ports 23 and 24 adjacent and posterior to throttles 13 and 14, when closed in the well-known manner. An adjustment 25 is provided for the primary idling system.

Secondary throttle valve 14 is unbalanced in such manner that the force of air flow passing through the secondary mixture conduit during operation tends to open this throttle. Secondary throttle control lever 18 has a lateral roller 30 at one extremity which engages an extended lobe 31 on primary throttle control lever 17,

while the primary throttle is closed and until it has nited States Patent opened a predetermined degree, for instance, 60. An eccentric weight 32 is secured to the other extremity of secondary throttle control crank 18 and normally urges the secondary throttle closed.

A tension spring 33 is stressed between lugs 34 and 35 on control levers 17 and 18 and is disposed with relation to these levers in such a manner as to apply its greatest resistance to opening of the secondary throttle when the primary throttle is fully closed. This spring stress causes a stop lug 36 on secondary throttle lever 18 to firmly engage stop screw 37 in a fixed rib 37' so as to accurately maintain the desired idling position of the secondary throttle. This is extremely important due to the multiplication of throttle valves since uncontrolled leakage around the throttle valves during idling materially aifects the idling speed of the engine. Such ill eifect of leakage is accentuated in the four-barrel, two-stage carburetors now widely used. Lug 38 on primary throttle lever 17 is held against its abutment screw 39 by the usual throttle return spring (not shown).

In operation, both throttle valves will be in their fully closed positions, as shown in Fig. 1, during idling. At this time, maximum force is applied to the secondary throttle through spring 33 tending to close it. This force, of course, must be insufficient to overcome the throttle return spring which holds the primary throttle valve closed. After the primary throttle valve has opened a predetermined degree, as shown in Fig. 2, lobe 31 passes downwardly beyond stop roller 30 on secondary control lever 18 so as to release this lever and the secondary throttle valve for partial opening under the influence of increasing air flow, as the engine speed increases, acting against the unbalanced secondary throttle valve acting against spring 33. The degree of possible opening of the secondary throttle valve increases as the primary throttle valve is opened and when primary throttle 13 is fully opened, secondary throttle 14 can fully open also. It will be noted that as the valves open, tension spring 33 is progressively shortened so that its tension as applied to the secondary throttle is decreased. During the latter part of the opening movement of the primary throttle, when the secondary throttle maybe opened by air-flow, spring 33 applies substantially less resistance thereto than in the idling position of the throttles. Spring '33, of course, aids in opening of the primary throttle while applying strong closing force to the secondary throttle during idling.

The particular type of carburetor shown, and the exact arrangement of the mixture conduits and leverages are not essential and these may be modified in various respects as will occur to those skilled in the art. The exclusive use of all modifications as come within the scope of the appended claims is contemplated.

We claim:

1. A two-stage carburetion system for internal combustion engines comprising primary and secondary mixture conduits, primary and secondary throttle valves, respectively, therein, manual means for controlling said primary throttle valve, said secondary throttle opening automatically in response to increasing speed of the associated engine with said primary throttle opened, and means variably resisting opening of said secondary throttle valve in accordance with the primary throttle position comprising first and second pivoted levers movable with their respective valves, and spring means stressed between and interconnecting said levers, said spring means being applied to said second lever so as to tend to close said secondary throttle valve and engaging a portion of said first lever which moves in a direction tending to decrease the stressing of said spring as said primary throttle is moved toward its opened position.

2. In a two-stage carburetion system for internal com- Patented Apr. 30, 1957 bustion engines, primary and secondary induction conduits having primary and secondary throttles, respectively, therein with primary and secondary pivoted levers movable, respectively, therewith in substantially planar relation with each other, manual means for opening said primary throttle and automatic means for yieldably opening said secondary throttle responsive to increasing air flow through said primary conduit as said primary throttle opens, and means variably resisting opening of said secondary throttle in accordance with positioning of said primary throttle comprising spring means stressed between said pivoted levers and applied to said secondary lever in the direction tending to close said secondary throttle valve and connected to a portion of said primary lever which moves in a direction tending to relax said spring as said primary throttle valve moves through a substantial range of open positions.

3. A two-stage carburetion system for internal combustion engines comprising primary and secondary induction conduits, primary and secondary throttles therein, manual means for controlling said primary throttle, said secondary throttle opening automatically responsive to air flow through said secondary conduit, actuating members movable with said throttle valves, a spring stressed between and interconnecting said members for constantly resisting opening of said secondary throttle with a force variable with primary throttle opening, and a one-Way operative connection between said valves for closing said secondary throttle when said primary throttle is closed.

4. A two-stage carburetion system comprising primary and secondary mixture conduits, primary and secondary throttle valves, respectively, therein, a control lever movable with each of said valves, said secondary valve being unbalanced so as to be opened by air flow thereagainst in operation, a stop device actuable with said primary throttle for preventing opening of said secondary throttle until said primary throttle has opened beyond a predetermined degree, and a spring stressed between and interconnecting said control levers and disposed to apply decreasing resistance to opening of said secondary valve as said primary valve is moved through a substantial range of open positions.

5. A two-stage carburetion system as described in claim 4 in which said stop device is included with said primary throttle control lever and cooperates with said secondary throttle control lever to limit opening of said secondary throttle.

6. A two-stage carburetion system as described in claim 4 in which said spring is disposed with relation to said control levers so as to apply maximum resistance to opening of said secondary throttle when said primary throttle is fully closed and minimum resistance thereto when said primary throttle is fully opened.

7. In a multi-stage carburetor, a manually controlled primary throttle, a secondary throttle automatically opened responsive to increased air flow, spring means yieldably resisting opening movement of said secondary throttle, and means operable responsive to opening movement of said primary throttle throughout a substantial range of primary throttle positions for variably decreasing the force exerted by said spring means in yieldably resisting opening movement of said secondary throttle.

8. A carburetor according to claim 7 in which said spring means is calibrated to balance said automatic secondary throttle in increasingly open positions as the air velocity in the carburetor increases.

9. A carburetor according to claim 7 in which said spring means is calibrated to balance said automatic secondary throttle in increasingly open positions as the air velocity in the carburetor increases, and a mechanical connection between said primary and secondary throttles for positively closing said secondary throttle as said primary throttle is closed.

10. In a two-stage carburetor, primary and secondary conduits, a manually controlled, normally closed primary throttle valve in said primary conduit, an unbalanced secondary throttle valve in said secondary conduit automatically opened responsive to increases in air flow in said secondary conduit, spring means interconnecting said throttle valves urging said primary throttle valve toward its open position and urging said secondary throttle valve toward its closed position.

11. In a two-stage carburetor, a manually controlled, normally closed primary throttle valve, an unbalanced econdary throttle valve automatically opened responsive to increases in air flow, spring means interconnecting said throttle valves urging said primary throttle valve toward its open position and urging said secondary throttle valve toward its closed position, and means operable responsive to opening movement of said primary throttle valve throughout a substantial range of primary throttle valve positions for variably decreasing the force exerted by said spring means.

12. In a two-stage carburetor, a manually controlled, normally closed primary throttle valve, an unbalanced secondary throttle valve automatically opened responsive to increases in air flow, spring means interconnecting said throttle valves urging said primary throttle valve toward its open position and urging said secondary throttle valve toward its closed position, means operable responsive to opening movement of said primary throttle valve for decreasing the force exerted by said spring means, and other means operative to positively close said secondary throttle valve responsive to closing movement of said primary throttle valve.

References Cited in the file of this patent UNITED STATES PATENTS 2,254,834 Betry Sept. 2, 1941 2,363,153 Shipman Nov. 21, 1944 2,420,925 Wirth May 20, 1947 2,640,472 Bicknell June 2, 1953 2,647,502 Braun Aug. 4, 1953 

